Security readout for executives and security teams
Plain-English summary
A race condition in Linux's SMC networking code can release connection resources more than once, leaving the kernel accessing freed memory. The supplied CVSS assessment rates potential confidentiality, integrity, and availability impact as critical. Actual organizational risk depends on whether affected kernels use the SMC subsystem.
Executive priority
Prioritize prompt assessment and patching because the supplied severity is critical and the flaw affects kernel memory safety. Focus first on SMC-enabled or SMC-dependent servers. There is no supplied evidence of active exploitation, so emergency incident response is not justified solely by this record.
Technical view
Unprotected calls to smc_conn_free() in the server listening path can duplicate LGR or link reference releases. Reference counts may reach zero prematurely, initiating cleanup while resources remain accessible. The kernel fix adds socket-lock protection in smc_listen_work() so connection cleanup is exclusive with competing operations.
Likely exposure
Potential exposure is limited to Linux systems running affected kernel versions where SMC networking is present and relevant listening activity occurs. The bundle identifies affected Linux versions but does not clearly define complete version ranges or exploitation prerequisites. Confirm exposure against distribution-specific advisories and installed kernel packages.
Exploitation context
The supplied CVSS vector describes remote, low-complexity, unauthenticated exploitation without user interaction. However, the bundle provides no exploit demonstration, attack details, or evidence of active exploitation, and the CVE is not listed as KEV. Treat practical exploitability as unconfirmed.
Researcher notes
CWE-416 applies. The reported failure involves competing cleanup paths calling smc_conn_free() and smcr_link_put(), producing reference-count underflow or addition on zero. The fix serializes smc_listen_work() cleanup with other connection operations using the socket lock. The sources do not establish reliable code-execution behavior or a complete affected-version boundary.
Mitigation direction
- Install the applicable vendor-supported kernel update containing the SMC locking fix.
- Consult distribution guidance to identify corrected packages for each deployed kernel branch.
- Prioritize systems that expose or actively use SMC networking.
- Apply normal change controls and reboot if required to activate the updated kernel.
Validation and detection
- Inventory installed and running kernel versions across Linux systems.
- Determine whether SMC networking is configured or used on potentially affected hosts.
- Compare kernel packages with vendor advisories and the referenced stable fixes.
- Review kernel logs for SMC-related refcount underflow or addition-on-zero warnings.
- After updating, verify systems booted into the corrected kernel.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
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ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-416: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2024-56640 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
2 official scoresWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9CISA-ADPVulnerability scoring details
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Base CVSS 3.1 score
7.8HighVector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://git.kernel.org/stable/c/f502a88fdd415647a1f2dc45fac71b9c522a052bCVE reference, Linux
- https://git.kernel.org/stable/c/0cf598548a6c36d90681d53c6b77d52363f2f295CVE reference, Linux
- https://git.kernel.org/stable/c/673d606683ac70bc074ca6676b938bff18635226CVE reference, Linux
- https://git.kernel.org/stable/c/6f0ae06a234a78ae137064f2c89135ac078a00ebCVE reference, Linux
- https://git.kernel.org/stable/c/2c7f14ed9c19ec0f149479d1c2842ec1f9bf76d7CVE reference, Linux
- https://lists.debian.org/debian-lts-announce/2025/03/msg00001.htmlCVE reference, CVE
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.